Electrical discharge tube



Dec. 11, 1934. R COHELD 1,9835% ELECTRICAL DI SCHARGB TUBE Filed July 29, 1932 2 Sheets-Sheet l 9 a2 5 I9 20 3o INVENTOR, PHIL/P F. SCOF/ELD. M r

ATTORNEY Dec. 11, 1934.

P. F. SCOFI ELD ELECTRICAL DISCHARGE TUBE Filed July 29; 1932 2 Sheets-Sheet 2 INVENTORT PHIL/P scar/51.0. B

ATTORNEY Patented Dec. 11, 1934 UNITED STATES PATENT OFFICE ELECTRICAL DISCHARGE TUBE Application July 29, 1932, Serial No. 625,869

Claims.

My invention relates to electrical discharge tubes having an electron-emitting cathode placed between a control electrode and a fluid-cooled anode, and more particularly to discharge tubes 5 of this kind adapted to handle large amounts of power for use, for example, in transmission stations for radio telegraphy or telephony.

Among the objects of my invention are: To provide an electrical discharge device capable of high power output; to provide a device which has a cathode interposed between the control electrode and a fluid-cooled anode; to provide a thermionic tube having a fluid-cooled anode positioned on its central axis; to provide a fluid-cooled anode sealed through an envelope, which will not crack the seal during operation; and to provide a high frequency oscillator and amplifier in which the cathode acts as a grounded shield between anode and control electrode.

Other objects of my invention will be apparent or will be specifically pointed out in the description forming a part of this specification, but I do not limit myself to the embodiment of my invention herein described, as various forms may be adopted within the scope of the claims.

Referring to the drawings:

Figure 1 is a sectional view of a tube embodying my invention, the plane of projection being indicated by the line 1-1 of Figure 2.

3 Figure 2 is a transverse sectional view of the tube, the plane of section being indicated by the line 2-2 of Figure 1.

In general terms my invention comprises a thermionic tube having an envelope in which is sealed a fluid-cooled anode. This anode is supported by one end of the envelope, and is mounted coaxially with the envelope of the device. A control electrode substantially cylindrical in shape and positioned within the envelope, concentrically surrounds the central anode. An electron-emitting cathode is interposed between the anode and control electrode.

A specific embodiment of my invention is shown (Cl. 25027.5) V

sembled so that two concentric channels are formed therein. An inner channel 5 and an outer channel 6 are separated by the insertion of an inlettube 7, which extends almost to the inner end of the anode and is welded to the anode at the 9 point of insertion. Shortly after the inlet tube passes the region of the seal, itis expanded to form an inlet shoulder 9, and is left with an open end 10 to allow contained fluid to pass freely into the outer channel 6. 10

The main body of the anode has an anode shoulder 11 which increases the diameter of the anode, and provides ample fluid space in the outer channel. In order to firmly support the inlet tube, a partition 12 extends from the base of the anode shoulder 11 to the bend of the inlet shoulder 9.

Holes 14 are provided in partition 12 to permit circulation through the anode. An exhaust port 15 is formed on the exterior end of the anode and is threaded to permit easy attachment to a drain, or a return pipe to a circulating supply. Likewise inlet port 16 on the exterior end of the inlet tube 7 is provided with threads to facilitate coupling to the circulating fluid system.

While the drawings show the inlet tube entering the anode at right angles, other ways of porting the anode will be apparent to those skilled in the art.

After the anode has been sealed in place, electrode arms 17, of the same material as the envelope, are fused to the side walls of the envelope. These arms have electrode supports 19 mounted in their distal ends, and held in place by the support seal 20. The electrode arms are in pairs, and the combination of three of such pairs formthe supporting structure of the complete control electrode. Yoke 21, spanning and connecting each pair of supports is screwed to the supports and is permanently joined and fixed in place by the small lock nuts 22. Holes 23 are provided in each end of the yoke whereby the individual control segment 24 may be attached by means of pins 25.

Each of these angular segments is made from. imperforate sheet metal, preferably tantalum, and extends the full length of the anode, stifiened at the outer edges by flanges 26. To further provide against buckling, reinforcing ribs 27 are applied to the major plane surface. Each segment may be assembled from two sections with center flanges 28 gripped by the yoke 21, or the entire segment may be formed from a single sheet with a fold for the center flange 28 where the yoke is applied. The pins 25 pass through the segments in exterior circuits, thus allowingthe tube to be used in a number of different ways.

be polygonal in shape to cooperate with the planar control surfaces, or thatthe control segments may be circular in shape, without departing from the spirit of my invention.

For protection, and ion-electrical:contact purposes, each arm is equipped with a connectioncap 29. The electrode supports are's'oldered or otherwise fastened to. the cap by-weld and the caps are maintained in'place by cement 31.

Interposed between the anode and the-controlelectrodes is a cathode, in this instance composed-- of a plurality of V-shaped filaments.32. .Thesefilaments are preferably of refractory material:

capable of emitting copious quantities of electrons when heated, such astungsten. The end.

of the envelope opposite the insertion of the The other arm is welded to a concentric metal. skirt sleeve 41 which is fastened to a skirt 42 extended from the reentrant stem 34.

Theapices of the filaments are resiliently sup-. ported by filament springs 44 fused at insertion 45 into an envelope ringv 46. which. surrounds the anode seal. .The insertion of these springs follows a method wellnknown in the. incandescent .lamp industry.

The V-shaped filaments are adjusted to a position that is preferably closer to the control electrode than to the anodeand the proper. tension is placed .onthe filament byadjustment of the fila--.

ment springs.

Y seal 50.

The skirt sleeve 41 is fiexibly connected to cathode lead 47 bythe extensible link 49. M This lead is brought through the envelope by a lead It will be seen that all of the filament-Vs are in parallel connection, and in tubes of high power the cathode leads are made large in diameter to prevent temperature rises cracking the lead seals. In operation, the cathodes are heated and the tube connected in a suitable circuit, and fluid,

preferably water; on account of its ch'eapness and availability, is circulated through the anode as in-' dicated by the arrows. By spacing the inlet tube away from the anode wall in the neighborhood of" the seal, cold water from the main supply does not come in contact with the seal. This greatly reduces strain at the seal and promotes long operating life.

While the amplification constant of the tube is relatively low, due to the position of the control electrode, the internal resistance is also low due to the unobstructed electron path, and large amounts of power are efficiently handled. At high -frequencies, used as an oscillator orsamplifier, the

filamentary cathode acts as a grounded screen or shield between anode and control electrode, and

high conversion efficiencies are obtained. The

It will also be obvious thati -the anode 2.1nayi 'operatingicharacteristics are comparable to those of the standard grid type tube havinga shield between grid-and plate, known in the art as a screen .grid J tube,-1Without the complexities in- Volved in such mum-element structure. Tubes-1.handling '5 kilowatts of power are small insize and economical to operate, especially when employing the higher frequencies.

I: claim:

, 1v. Anelectrical discharge deviceihaving an-envelope, ai-central fluid cooledanode mounted co axially-with said envelope, a plurality of electriacally :separatedssections of a control electrode polygonally arranged around said anode, and an electron emitting cathode interposed between said sections of acontrol electrode and-said anode.

2.. electrical discharge tube having --an. en-

velope, a. hollow anode'sealed through one end of" .said. envelope, concentric channels formed in- -tegrally with'said anode Within said anode for directingthe-fiow of a circulated fluid, aplurality of planarcontrol electrodes polygonally arranged around. said anode, and a plurality of filamentary conductors capable of emitting electrons when heated interposed i between said anode :andsaid controlelectrodes.

3. An electrical dischargedevice, anenvelope,

a stemfused to oneend of said envelope, a central fluid-cooled anode sealed through said stem and mounted coaxially with said envelope, a stepped creentrantstem in the opposite end of-said-envelope, a cathode circumjacent. said anode supported atritslower end by said 'reentrant stem-and a plurality of planar-control electrodes arranged aroundsaid anode, each of said control electrodes :beingsupported within the envelope-bytheside walls thereof.

Anelectrical discharge device-having an en velope, a central fluid-cooled anodeamounted. coaxially with said envelope, a plurality of separate controlelectrode sections arranged around said anode, each of said sections being separately supported within the envelope by the sidewalls there-"-- .of, and an electron-emitting cathode interposed between each of .saidsections and said'anode. 5..Anelectrical discharge devicehaving. an envelope, a central fluid-cooled anode mounted coaxially with said envelope, a plurality of separate control electrode sections arranged around said "anode; said sections being spaced apart and adapted to be separately connectedtoan" external electrical circuit," and an'electron emitting cathode interposed between each of said sections and said anode.

l PHILIP F. SCOFIELD. 

